1. Technical Field
The invention relates to a protective safety shield for use in the electrical industry. More particularly, the invention relates to a safety shield that may be clamped to different diameter racking rods and can be used to protect workers from electrical arcs, flashes and fragmentation explosions which can occur while opening and closing circuit breakers.
2. Background Information
Tripping and resetting electrical circuit breakers can pose a serious threat of injury to electrical workers because of the potential risk of the occurrence of electrical arcs, electric flashes and fragmentation explosions. These arcs, flashes or explosions are capable of causing electrical burns, molten metal burns and flesh wounds caused by flying debris.
Circuit breakers are typically mounted in a protective cabinet. In order to perform routine maintenance and repair, the worker has to open the cabinet and, using a racking rod, shift the breakers either vertically or horizontally in order to disconnect them from the power source. The breakers are then removed from the cabinet and the necessary maintenance or repair is performed. When the work is completed, the breakers are replaced in the cabinet and then, using the racking rod, are moved either vertically or horizontally back into connection with the power source. Both the tripping and resetting require the worker to be located close enough to reach the cabinet with the racking rod and this puts them at risk because the circuit is energized when it is tripped and become energized when it is being reset.
Various devices have been proposed in the art to assist and protect the worker during the tripping and resetting of the breaker. These devices have included different types of hot sticks, eye protection, hard hats, flame retardant clothing and gloves. Yet other devices have included mechanized systems for moving and placing breakers in order to allow the worker to remain at a slightly safer distance from the equipment. There is, however, no way for the worker to maintain a completely safe distance when the breakers are tripped and reset.
U.S. Pat. No. 5,666,253, assigned to the present assignee, discloses a shield that physically protects linemen using a hot stick as they work. The shield protects the worker from electrical arcs, electrical flashes and fragmentation explosions and from objects and debris produced during the pulling of pad-mounted switches, the insertion of fuses into overhead transformers or numerous other applications. This shield includes a plate formed of a transparent material and a clamping means for removably mounting the plate to the hot stick. However, the hot sticks used in conjunction with the device proposed by this patent are long and of a fairly large diameter. They are therefore not suitable for opening breaker circuits in more cramped quarters. Tripping and resetting breakers requires the use of racking rods and depending on the application, racking rods of different diameters may need to be utilized. All of these racking rods are significantly smaller in diameter than the hot sticks used for working on overhead lines.
There is therefore a need in the art for a protective shield that can be used in conjunction with a plurality of different diameter hot sticks or racking rods for tripping and resetting differently sized circuit breakers in close quarters.